In various types of imaging apparatus, a photographic film must be clamped in a workstation while a particular operation is performed on the film. In certain types of apparatus, for example, film scanners, the film must be held extremely flat in order for an image on the film to be recorded properly. One problem in maintaining the film flat is that photographic film has a natural curl due to an emulsion coated on one side of the film. In one known type of film gate, a film is clamped against a flat platen, and the film and platen are moved relative to an image sensor to scan the film. In the use of such a film gate, the film must be clamped and unclamped for each film frame, and the film platen must be moved to a home position after each frame is scanned. Such a technique requires a significant number of moving parts, and it is relatively slow. Further, devices of this type are likely to scratch the film, and the motion of the platen introduces the possibility of vibrations into the system.
It is also known to use a rotary film gate, as disclosed, for example, in U.S. Pat. No. 4,281,351. U.S. Pat. No. 4,281,351 discloses apparatus for the line-by-line optical scanning of a film. In order to reduce friction of the film adjacent the scanning region, rollers or endless belts support the film at positions on the film outside of the film frames. A disadvantages of the apparatus disclosed in this patent is that the only means for maintaining the film flat in the scan region is through the tension in the film. Thus, any irregular motion in the drive system is transmitted to the film, and this tends to produce blurring in the scanned image. A further disadvantage is that elements of the drive mechanism for the rotary film gate are arranged such that a relatively complex optical arrangement must be used to provide light to an imaging station in the film gate.